U.S. Pat. No. 6,212,722 proposes an improved laundry washing machine for domestic use. This machine is of the top loading type having an outer bowl, a wash basket within the outer bowl and access to the wash basket through a top opening. A motor is provided to drive rotation of the wash basket within the outer bowl. A wash plate is provided in the lower portion of the wash basket to be rotated by the motor with the wash basket or independently of the wash basket. The patent proposes a combination of water level control, wash plate design, wash basket design and movement pattern for the wash plate which leads to an inverse toroidal movement of the laundry load during a wash phase. The sodden wash load is dragged by friction radially inward on the upper surface of the wash plate and progresses upward in the region of the centre. The sodden wash load then progresses radially outward to the wall of the wash basket and downward to the base of the wash basket. This has been found to provide an effective wash action with low water consumption.
The patent indicates that this is only achieved at water levels within a determinable band. With too much water the inverse toroidal rollover motion is not achieved because the clothes lose frictional contact with the wash plate.
The present inventors have ascertained a desire to include an effective wash mode that sacrifices a degree of water efficiency in favour of dilution of the wash solution. The inventors consider this to be particularly desirable in the case of heavily soiled laundry items or laundry items having insoluble soiling, such as muddy, sandy or grass covered sports clothes, and in the case of laundry subject to dye leakage.
The inventors consider that the laundry machine described in U.S. Pat. No. 6,212,722 is only partially effective in this regard. At higher water levels in which the machine cannot perform the inverse toroidal rollover pattern the inventors consider the machine is likely to provide a less effective wash action. The effect of inverse toroidal wash action by dragging is only available at low water levels, and there is a middle water level at which no rollover occurs. Where the laundry load does not rollover wash action of clothing against the wash plate is limited to a small fraction of the load and wash performance suffers.